mirror of
https://github.com/Jermolene/TiddlyWiki5
synced 2024-12-04 23:39:57 +00:00
6af3eb539b
* Initial widget tutorials extracted from https://btheado.github.io/tw-widget-tutorial/ * Fixes for refresh behavior change
51 lines
2.8 KiB
Plaintext
51 lines
2.8 KiB
Plaintext
created: 20190202035425715
|
|
modified: 20190205023518575
|
|
tags:
|
|
title: Widget attributes tutorial part I
|
|
type: text/vnd.tiddlywiki
|
|
|
|
So far none of the widgets we've implemented have had any code for handling widget attributes A vast majority of useful widgets will need to support attributes in order to make them useful.
|
|
|
|
As an example, let's change the Hello World widget so it can greet not just the world, but whoever/whatever the user wants. To do that we can add support for an attribute named `what` and call it like `<$hello what="pale blue dot"/>`.
|
|
|
|
The tiddlywiki widget class provides methods `computeAttributes` and `getAttribute` which can together be used by the widget code to discover what values are passed into the widget.
|
|
|
|
The `computeAttributes` and `getAttribute` methods can be called like this (the second parameter to `getAttribute` will be used as the default value if the user doesn't provide that attribute in the widget call):
|
|
|
|
```javascript
|
|
this.computeAttributes();
|
|
var message = this.getAttribute("message", "World");
|
|
```
|
|
|
|
Then the `message` variable can be used to construct the Hello XXX string:
|
|
|
|
```javascript
|
|
var textNode = this.document.createTextNode("Hello, " + message + "!");
|
|
```
|
|
|
|
The original [[hello.js]] code only implements a `render` method. The `refresh` method is not needed because the output from the widget can never be different...it will always be "Hello, World!".
|
|
|
|
Even with a `message` attribute, you might think the `render` by itself is enough. After all, the value of the input parameter `message` can only be changed by modifying the wiki text which means the tiddler will be redisplayed from scratch.
|
|
|
|
However, tiddlywiki has a syntax which allows parameter values to vary without modifying the wiki text. See https://tiddlywiki.com/#Widgets%20in%20WikiText for details. As one example, if the widget were called like `<$hello message={{MyTiddler!!field}}/>`, then every time the `field` field of `MyTiddler` were modified, only the `refresh` method would be called. Therefore, in order to get the widget display to update, the refresh method needs to be implemented.
|
|
|
|
If the `computeAttributes` and `getAttribute` calls are placed in the `render` method then we can implement a performance unoptimized version of refresh as was done in [[Widget refresh tutorial part II]]:
|
|
|
|
```javascript
|
|
/*
|
|
A widget with optimized performance will selectively refresh, but here we refresh always
|
|
*/
|
|
MyWidget.prototype.refresh = function(changedTiddlers) {
|
|
// Regenerate and rerender the widget and
|
|
// replace the existing DOM node
|
|
this.refreshSelf();
|
|
return true;
|
|
};
|
|
```
|
|
|
|
The full code can be seen at [[hello-attribute.js]] and here is the result ([[Widget attributes demo I]]):
|
|
|
|
{{Widget attributes demo I}}
|
|
|
|
The third example above is the only one which requires the refresh method in order to behave properly.
|